Various medical implants depend upon closed hydraulic systems to maintain a desired working pressure in a pressure chamber for extended periods of time. The artificial sphincter system shown and described in Burton U.S. Pat. No. 4,222,377 is one example of such an implant and the penile implant shown in my earlier U.S. Pat. No. 4,369,771 is another. In the Burton device, the pressure exerted by a pressure chamber in the form of an inflatable cuff is relied upon to keep a body passage closed and in an inflatable penile implant a pressure chamber in the form of a non-distensible cylindrical chamber is pressurized to make it rigid and to make the penis assume an erectible state.
When an implanted medical implant fails to function properly it must be surgically removed and replaced. Therefore, medical implants are carefully made of the finest materials. However, because of the extremely low hydraulic fluid capacitance of such systems and potential leak paths within such systems, minor leakage may occur and any leakage, no matter how slight, can result in a rapid decrease in system pressure causing the implant to fail to function as designed, and requiring its replacement.
In artificial sphincter systems, it is possible, as seen in the forementioned Burton patent, to compensate for minor leaks within the hydraulic system by providing a pressure regulating balloon which is implanted in the abdominal cavity. It would be advantageous to have some smaller effective means of compensating for leaks than the large balloon. The penile implants are intended to be self contained and to be implanted completely within the penis. There is no place in such an implant for a relatively large artificial sphincter type pressure regulating balloon.
There is a need for a small and an effective means of compensating for minor leakages and preventing pressure drops within the hydraulic system of a medical implant which depends upon the maintenance of a pressure in a pressure chamber for extended periods to provide its desired function.